QmlJS checks: Add confusing +/- check.

Migrated from QtChecker.

Change-Id: I06115152f979f9abfa9cbdf4a3e2e63a51ea7284
Reviewed-on: http://codereview.qt-project.org/5858
Reviewed-by: Fawzi Mohamed <fawzi.mohamed@nokia.com>
Sanity-Review: Qt Sanity Bot <qt_sanity_bot@ovi.com>

src/libs/qmljs/qmljscheck.cpp

@@ -873,6 +873,35 @@ bool Check::visit(BinaryExpression *ast)
             addMessage(MaybeWarnEqualityTypeCoercion, ast->operatorToken);
         }
     }
+
+    // check odd + ++ combinations
+    const QLatin1Char newline('\n');
+    if (ast->op == QSOperator::Add || ast->op == QSOperator::Sub) {
+        QChar match;
+        Type msg;
+        if (ast->op == QSOperator::Add) {
+            match = QLatin1Char('+');
+            msg = WarnConfusingPluses;
+        } else {
+            QTC_CHECK(ast->op == QSOperator::Sub);
+            match = QLatin1Char('-');
+            msg = WarnConfusingMinuses;
+        }
+
+        if (int(op.end()) + 1 < source.size()) {
+            const QChar next = source.at(op.end());
+            if (next.isSpace() && next != newline
+                    && source.at(op.end() + 1) == match)
+                addMessage(msg, SourceLocation(op.begin(), 3, op.startLine, op.startColumn));
+        }
+        if (op.begin() >= 2) {
+            const QChar prev = source.at(op.begin() - 1);
+            if (prev.isSpace() && prev != newline
+                    && source.at(op.begin() - 2) == match)
+                addMessage(msg, SourceLocation(op.begin() - 2, 3, op.startLine, op.startColumn - 2));
+        }
+    }
+
     return true;
 }
 

src/libs/qmljs/qmljsstaticanalysismessage.cpp

@@ -146,12 +146,8 @@ StaticAnalysisMessages::StaticAnalysisMessages()
            tr("do not use void expressions"));
     newMsg(WarnConfusingPluses, Warning,
            tr("confusing pluses"));
-    newMsg(WarnConfusingPreincrement, Warning,
-           tr("confusing preincrement"));
     newMsg(WarnConfusingMinuses, Warning,
            tr("confusing minuses"));
-    newMsg(WarnConfusingPredecrement, Warning,
-           tr("confusing predecrement"));
     newMsg(HintDeclareVarsInOneLine, Hint,
            tr("declare all function vars on a single line"));
     // unused

src/libs/qmljs/qmljsstaticanalysismessage.h

@@ -88,9 +88,7 @@ enum Type
     WarnBlock = 115,
     WarnVoid = 116,
     WarnConfusingPluses = 117,
-    WarnConfusingPreincrement = 118,
     WarnConfusingMinuses = 119,
-    WarnConfusingPredecrement = 120,
     HintDeclareVarsInOneLine = 121,
     HintExtraParentheses = 123,
     MaybeWarnEqualityTypeCoercion = 126,